Originations of non-agency jumbo mortgages are stronger than the overall market, big banks are competing for wealthy borrowers and smaller firms are looking to enter the market. While jumbos originated in recent years have performed exceptionally well, Standard & Poor’s stresses that lenders should control their growth. “In our opinion, controlled growth is a key aspect to the comprehensiveness and ultimate success of an originator’s business strategy,” the rating service said in a recent overview of jumbo performance and best practices. “We believe that aggressive growth strategies could result in difficulties managing the quality of the origination process.” S&P noted...